Room-temperature rechargeable Na-SO2 batteries containing a gel-polymer electrolyte.

We constructed rechargeable Na-SO2 batteries, based on a NaI redox mediator and containing a gel-polymer electrolyte and a multiwall carbon nanotube@Ni foam porous cathode, with a newly demonstrated battery reaction, specifically 2Na + 2SO2 ↔ Na2S2O4. A large reversible capacity of 5000 mA h g-1 at 200 mA g-1 (763 W h kg-1) and a high capacity retention of nearly 100% after 100 cycles were obtained.